Electromechanical force microscopy and tip-enhanced raman spectroscopy on polar oxide nanoparticles

Röhrig, Serge

Dissertation / PhD Thesis/Book

Electromechanical force microscopy and tip-enhanced raman spectroscopy on polar oxide nanoparticles

Röhrig, S. (Corresponding author)FZJ*

2009
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-600-2

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Information / Information 7, VI, 114 S. (2009) = RWTH Aachen, Diss., 2009

Please use a persistent id in citations: http://hdl.handle.net/2128/7194

Abstract: This work comprises two major parts, one devoted to electromechanical force microscopy that will be summarized first and a second one dealing with tip-enhanced Raman spectroscopy that will be summarized thereafter. • $\textbf{Piezoresponse Force Microscopy}$ Several different material systems were investigated by PFM providing insight into local structures of hollow BaTiO$_{3}$ particles and ferroelectric ordering in NaNbO$_{3}$. The geometrical constraints of the tip curvature to the imaging quality of PFM at the perimeter of ferroelectric nanoislands is shortly discussed. • $\textbf{Dynamic PFM}$ Exceeding the coercive field upon scanning within the piezoresponse force mode results in a loss of the domain imaging contrast. In exchange, it provides highly rewarding data on the nature of the electrical contact and its dynamics that are used to propose a novel detection scheme for ferroelectric domain reversal and a new method to estimate ferroelectricity in thin structures without a restriction due to the coercive field. • $\textbf{Adsorbate-induced phase shift in PFM experiments}$ Adsorbates are modeled by a voltage divider. This work incorporates them as part of the realistic AC-circuit. As a function of frequency, the domain-dependent RC-time constants contribute another, sometimes dominant, term to the existing theory of the phase difference. • $\textbf{Electromechanical Force microscopy}$ Polar and nonpolar surfaces can be imaged for local dielectric heterogeneities by a novel scanning probe microscopy technique at 2 ω that has been filed as a patent. The feasibility is demonstrated on misfit dislocations of relaxed BaTiO3 on a SrTiO$_{3}$ (100) surface. The data are in excellent quantitative agreement with FEM simulations of the defect signature and independent studies of the dislocation density and ordering. • $\textbf{Tip-enhanced Raman microscopy}$ During this work two tip-enhanced Raman microscopes were set up, one for use under ambient conditions, another one for use in UHV. Both of them are designed for resonant excitation of gold and silver nanoparticles at the respective wavelengths. Successful operation under ambient conditions was demonstrated with a typical enhancement factor of 5·10$^{4}$. The system is characterized for UHV conditions in terms of beam diameter, numerical aperture, photon efficiency, and operation with the multichannel analyzer of the Raman spectrometer. Confocal Raman measurements under UHV conditions confirmed the calculated photon efficiency.

Note: Record converted from VDB: 12.11.2012
Note: RWTH Aachen, Diss., 2009

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